Transparent display device and method of manufacturing the same

ABSTRACT

A transparent display device including a base substrate and a plurality of pixels disposed on the base substrate, each pixel having an emission area and a transmission area transparent to external light, each of the pixels including a circuit element layer disposed on the base substrate, a first electrode disposed on the circuit element layer and corresponding to the emission area, a pixel define layer disposed on the circuit element layer, the pixel define layer including a first sidewall defining the emission area and a second sidewall defining the transmission area, an emission layer disposed on the first electrode and corresponding to the emission area, and a second electrode disposed on the emission layer and including an opening that corresponds to the transmission area, in which the first sidewall is inclined at a first angle, and the second sidewall is inclined at a second angle greater than the first angle.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2019-0021366, filed on Feb. 22, 2019, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND Field

Exemplary embodiments of the invention relate generally to a transparentdisplay device and a method of manufacturing the same, and, morespecifically, to a transparent display device with an improvedtransmittance and a method of manufacturing the same.

Discussion of the Background

A display device is an apparatus that displays an image, and an organiclight-emitting display device has recently been receiving attention. Theorganic light-emitting display device has excellent characteristics,such as lower power consumption, higher luminance, and quicker fastresponse speed than a conventional display device.

An organic light-emitting display device may include a transparentlight-emitting display panel and have transparent properties. Thetransparent light-emitting display panel may include pixels each havinga transmission area that allows light to pass therethrough. As such,users can recognize an image displayed through the pixels of the displaypanel, as well as perceiving objects or images behind the display panelby light passing through the transmission areas.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Transparent display devices constructed according to exemplaryembodiments of the invention an a method of manufacturing the same havean improved transmittance.

Additional features of the inventive concepts will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the inventive concepts.

A transparent display device according to an exemplary embodimentincludes a base substrate and a plurality of pixels disposed on the basesubstrate, each pixel having an emission area and a transmission areatransparent to external light. The each pixel comprises a circuitelement layer disposed on the base substrate, a first electrode disposedon the circuit element layer and corresponding to the emission area, apixel define layer disposed on the circuit element layer, the pixeldefine layer including a first sidewall defining the emission area and asecond sidewall defining the transmission area, an emission layerdisposed on the first electrode and corresponding to the emission area,and a second electrode disposed on the emission layer and including anopening that corresponds to the transmission area. The first sidewall isinclined at a first angle and the second sidewall is inclined at asecond angle greater than the first angle.

A method of manufacturing a transparent display device including aplurality of pixels each having an emission area and a transmission areathat is transparent to external light according to another exemplaryembodiment includes the steps of forming a circuit element layer on atop surface of a base substrate, forming a first electrode correspondingto the emission area on the circuit element layer, forming a pixeldefine layer defining the emission area and the transmission area on thecircuit element layer, forming a preliminary organic layer correspondingto the emission area and the transmission area on the first electrode,forming an electrode layer covering the preliminary organic layer,heating up a portion of the preliminary organic layer disposed on thetransmission area to separate the portion of the preliminary organiclayer from the circuit element layer, and removing the portion of thepreliminary organic layer separated from the circuit element layer and aportion of the electrode layer to form an organic layer and a secondelectrode, each of the organic layer and the second electrode having anopening corresponding to the transmission area.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theinventive concepts.

FIG. 1 is a front view of a transparent display device according to anexemplary embodiment.

FIG. 2 is a cross-sectional view exemplarily showing a transparentdisplay device according to an exemplary embodiment.

FIG. 3 is a plan view of a pixel structure of a transparent displaypanel according to an exemplary embodiment.

FIG. 4 is a cross-sectional view taken along line I-I′ of FIG. 3,showing a display element layer of the transparent display panel of FIG.3.

FIG. 5 is an enlarged view showing section II of FIG. 4.

FIG. 6 is a cross-sectional view of a transparent display panelaccording to an exemplary embodiment.

FIG. 7 is an enlarged view of section III of FIG. 6.

FIG. 8 is a plan view showing a circuit configuration of each pixel of atransparent display panel according to an exemplary embodiment.

FIGS. 9A, 9B, 9C, 9D, 9E, 9F, and 9G are cross-sectional views showing amethod of manufacturing a transparent display device according to anexemplary embodiment.

FIGS. 10A, 10B, and 10C are enlarged cross-sectional views showingsection IV of FIGS. 9D to 9F, respectively.

FIGS. 11A, 11B, and 11C are cross-sectional views showing a method offorming a pixel define layer of FIG. 9C.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments or implementations of theinvention. As used herein “embodiments” and “implementations” areinterchangeable words that are non-limiting examples of devices ormethods employing one or more of the inventive concepts disclosedherein. It is apparent, however, that various exemplary embodiments maybe practiced without these specific details or with one or moreequivalent arrangements. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring various exemplary embodiments. Further, various exemplaryembodiments may be different, but do not have to be exclusive. Forexample, specific shapes, configurations, and characteristics of anexemplary embodiment may be used or implemented in another exemplaryembodiment without departing from the inventive concepts.

Unless otherwise specified, the illustrated exemplary embodiments are tobe understood as providing exemplary features of varying detail of someways in which the inventive concepts may be implemented in practice.Therefore, unless otherwise specified, the features, components,modules, layers, films, panels, regions, and/or aspects, etc.(hereinafter individually or collectively referred to as “elements”), ofthe various embodiments may be otherwise combined, separated,interchanged, and/or rearranged without departing from the inventiveconcepts.

The use of cross-hatching and/or shading in the accompanying drawings isgenerally provided to clarify boundaries between adjacent elements. Assuch, neither the presence nor the absence of cross-hatching or shadingconveys or indicates any preference or requirement for particularmaterials, material properties, dimensions, proportions, commonalitiesbetween illustrated elements, and/or any other characteristic,attribute, property, etc., of the elements, unless specified. Further,in the accompanying drawings, the size and relative sizes of elementsmay be exaggerated for clarity and/or descriptive purposes. When anexemplary embodiment may be implemented differently, a specific processorder may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order. Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z-axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z” and “at least oneselected from the group consisting of X, Y, and Z” may be construed as Xonly, Y only, Z only, or any combination of two or more of X, Y, and Z,such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various exemplary embodiments are described herein with reference tosectional and/or exploded illustrations that are schematic illustrationsof idealized exemplary embodiments and/or intermediate structures. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should notnecessarily be construed as limited to the particular illustrated shapesof regions, but are to include deviations in shapes that result from,for instance, manufacturing. In this manner, regions illustrated in thedrawings may be schematic in nature and the shapes of these regions maynot reflect actual shapes of regions of a device and, as such, are notnecessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

FIG. 1 is a front view of a transparent display device according to anexemplary embodiment. FIG. 2 is a cross-sectional view exemplarilyillustrating a transparent display device according to an exemplaryembodiment. FIG. 3 is a plan view of a pixel structure of a transparentdisplay panel according to an exemplary embodiment.

Referring to FIG. 1, a transparent display device DD may have a displayarea DA and a non-display area NDA defined thereon. The display area DA,on which an image IM is displayed, may be parallel to a plane defined bya first direction DR1 and a second direction DR2 intersecting the firstdirection DR1. In some exemplary embodiments, the first direction DR1may be parallel to a short side of the transparent display device DD,and the second direction DR2 may be parallel to a long side of thetransparent display device DD.

A user may recognize the image IM displayed on the display area DA, andmay further recognize an object or image behind the transparent displaydevice DD. FIG. 1 exemplarily illustrates that the transparent displaydevice DD displays a user's hand UH positioned on a backside thereof.

The transparent display device DD may be used for large-sized electronicapparatuses, such as televisions, monitors, and outdoor billboards, andmay also be used for small- and medium-sized electronic apparatuses,such as personal computers, laptop computers, personal digitalterminals, automobile navigation units, game consoles, portableelectronic devices, and cameras. However, the inventive concepts are notlimited thereto, and the transparent display device DD may be adoptedfor various other electronic apparatuses.

The non-display area NDA is a region that adjoins the display area DAand may not display an image IM. The non-display area NDA may define abezel region of the transparent display device DD. An object or imagebehind the non-display area NDA of the transparent display device DD maynot be recognized.

The non-display area NDA may surround the display area DA.Alternatively, the non-display area NDA may be partially adjacent to anedge of the display area DA or may be omitted. However, the inventiveconcepts are not limited thereto.

Referring to FIGS. 1 and 2, the transparent display device DD mayinclude a transparent display panel DP. The transparent display panel DPmay be a flexible display panel. For example, the transparent displaypanel DP may be flexible, and thus, the shape thereof may be changed bybending, folding, rolling, etc. In some exemplary embodiments, thetransparent display panel DP may be an organic light-emitting displaypanel including an organic light-emitting device.

The transparent display panel DP may include a base substrate BS and adisplay unit DM provided on the base substrate BS. The display unit DMmay include a light-emitting layer that emits internal light. Thelight-emitting layer may be provided to correspond to an emission areaEA. As such, the transparent display panel DP may display an imagethrough a plurality of emission areas EA. The transparent display panelDP may allow external light to pass through a transmission area TA.Accordingly, the transparent display panel DP may show an object orimage positioned on the backside thereof, while displaying an imagethrough the emission area EA.

The display unit DM may be provided with various devices and connectionlines corresponding to the emission area EA, and thus, external lightincident onto the emission area EA may have an extremely lowtransmittance or may hardly pass through the emission area EA. However,the various devices and connection lines may not correspond to thetransmission area TA, which may increase transmittance of external lightin the transmission area TA.

Although FIG. 2 shows a structure in which the transmission area TA isprovided directly adjacent to the emission area EA, in some exemplaryembodiments, a non-emission area (e.g., NEA of FIG. 3) may further beprovided between the emission area EA and the transmission area TA.

Referring to FIG. 3, the transparent display panel DP may include aplurality of pixels. Each of the plurality of pixels may include anemission area EA, a non-emission area NEA, and a transmission area TA.FIG. 3 shows two neighboring pixels PX1 and PX2 among the plurality ofpixels. The two pixels PX1 and PX2 may have substantially the sameconfiguration as each other. In addition, each of the pixels may havesubstantially the same configuration.

Each of the pixels PX1 and PX2 may include a plurality of sub-pixels.The emission area EA may include a plurality of emission areas EA1, EA2,and EA3 that respectively correspond to the plurality of sub-pixels. Thetransmission area TA may be disposed adjacent to the plurality ofemission areas EA1, EA2, and EA3.

According to the illustrated exemplary embodiment, each pixel mayinclude a first sub-pixel that displays a red color R, a secondsub-pixel that displays a green color G, and a third sub-pixel thatdisplays a blue color B. The first to third sub-pixels may havesubstantially the same size, or at least one of the first to thirdsub-pixels may have a different size from those of other sub-pixels. Asillustrated in FIG. 3, the third sub-pixel may have a size greater thanthose of the first and second sub-pixels. In this case, the thirdemission area EA3 corresponding to the third sub-pixel may have a sizegreater than those of the first and second emission areas EA1 and EA2corresponding to the first and second sub-pixels, respectively.

The transmission area TA may have a size greater than a sum of the firstto third sub-pixels. However, the inventive concepts are not limitedthereto, and in some exemplary embodiments, the size of the transmissionarea TA may be variously changed based on a desired transmittance of thetransparent display device DD.

FIG. 3 illustrates that each of the pixels PX1 and PX2 has onetransmission area TA, however, the inventive concepts are not limitedthereto. In some exemplary embodiments, each of the pixels PX1 and PX2may have a plurality of transmission areas TA. For example, each pixelmay include two or more transmission areas that respectively correspondto the first to third sub-pixels.

FIG. 3 shows that each of the emission areas EA1, EA2, and EA3 has asubstantially rectangular shape defined by the first and seconddirections DR1 and DR2. However, the inventive concepts are not limitedthereto. For example, each of the emission areas EA1, EA2, and EA3 mayhave a substantially rhombohedral shape. The transmission area TA isalso illustrated to have a substantially rectangular shape defined bythe first and second directions DR1 and DR2, but the shape of thetransmission area TA may be changed based on each shape of the emissionareas EA1, EA2, and EA3.

The transparent display device DD shown in FIGS. 1 to 3 is illustratedas having a structure in which each of the pixels PX1 and PX2 isprovided with the transmission area TA, but the inventive concepts arenot limited thereto. For example, the display area DA of the transparentdisplay device DD in some exemplary embodiments may be partiallyconstructed as a transparent display region. In this case, thetransmission area TA may be provided on pixels disposed on thetransparent display region, and pixels disposed in regions other thanthe transparent display region may not include the transmission area TA.In this manner, on the transparent display region, the emission area EAmay display an image and the transmission area TA may display an objector external image behind the transparent display device DD, but on otherdisplay regions, only the emission area EA may display an image.

FIG. 4 is a cross-sectional view taken along line I-I′ of FIG. 3,showing a display element layer of the transparent display panel of FIG.3. FIG. 5 illustrates an enlarged view of section II of FIG. 4.

Referring to FIGS. 4 and 5, the transparent display panel DP may includea base substrate BS and a display unit DU, which may include a circuitelement layer CL, a display element layer DPL, and an encapsulationlayer TFE. In some exemplary embodiments, the display unit DU mayfurther include one or more of a touch sensor, anti-reflection layer,and a window.

The base substrate BS may be a silicon substrate, a plastic substrate, aglass substrate, a dielectric film, or a stack structure including aplurality of dielectric layers.

The circuit element layer CL may include a sub-pixel circuit provided oneach sub-pixel and a plurality of signal lines SL connected to thesub-pixel circuit. The sub-pixel circuit may include a plurality oftransistors TR and a capacitor. FIG. 4 exemplarily shows one transistorTR, but the inventive concepts are not limited to a particular numberand structure of the transistor TR. The circuit element layer CL mayinclude a barrier layer BR, an active layer ACT, a gate insulating layerGI, a gate electrode GE, an interlayer insulating layer ILD, an inputelectrode SE, an output electrode DE, and an intermediate insulatinglayer VLD.

The barrier layer BR may be disposed on the base substrate BS and mayprevent foreign substances from infiltrating onto the barrier layer BR.In some exemplary embodiments, the display unit DU may further include abuffer layer on the barrier layer BR. The buffer layer may increasebonding strength between the base substrate BS and layers disposed onthe base substrate BS. The barrier layer BR and the buffer layer may beoptionally disposed or omitted.

The active layer ACT may be disposed on the barrier layer BR. The activelayer ACT may serve as a channel region of the transistor TR. The activelayer ACT may include one selected from amorphous silicon, polysilicon,and oxide semiconductor.

The gate insulating layer GI may be disposed on the active layer ACT.The gate insulating layer GI may insulate the gate electrode GE from theactive layer ACT.

The gate electrode GE may be disposed on the gate insulating layer GI.The gate electrode GE may be placed to overlap the active layer ACT. Afirst conductive layer forming the signal lines SL may be disposed atthe same level as that of the gate electrode GE.

The interlayer insulating layer ILD may be disposed on the gateelectrode GE. The interlayer insulating layer ILD may electricallyinsulate the gate electrode GE from the input and output electrodes SEand DE. The interlayer insulating layer ILD may include an inorganicmaterial. The inorganic material may include silicon nitride, siliconoxynitride, silicon oxide, or the like.

The input and output electrodes SE and DE may be disposed on theinterlayer insulating layer ILD. Each of the input and output electrodesSE and DE may be electrically connected to the active layer ACT througha corresponding one of first and second contact holes CH1 and CH2provided in the interlayer insulating layer ILD and the gate insulatinglayer GI. A second conductive layer forming the signal lines SL may bedisposed at the same level as that of the input and output electrodes SEand DE.

The transparent displayer panel DP according to the illustratedexemplary embodiment is described as having a top-gate structure, inwhich the gate electrode GE is disposed above the active layer ACT, butthe inventive concepts are not limited thereto. In some exemplaryembodiments, the transparent display panel DP may have a bottom-gatestructure, in which the gate electrode GE is disposed beneath the activelayer ACT. In yet other exemplary embodiments, the transparent displaypanel DP may include one of a plurality of transistors TR having thetop-gate structure and another one of the plurality of transistors TRhaving the bottom-gate structure.

The intermediate insulating layer VLD may be disposed on the input andoutput electrodes SE and DE. The intermediate insulating layer VLD mayprovide a planarized surface. The intermediate insulating layer VLD mayinclude an organic material. The organic material may include one ormore of acryl-based resin, methacryl-based resin, vinyl-based resin,epoxy-based resin, urethane-based resin, cellulose-based resin,siloxane-based resin, polyimide-based resin, polyamide-based resin, andperylene-based resin.

The display element layer DPL may be disposed on the intermediateinsulating layer VLD. The display element layer DPL may include a pixeldefine layer PDL and a plurality of display elements OLED. The pluralityof display elements OLED may be correspondingly provided on theplurality of sub-pixels, and may be connected to corresponding sub-pixelcircuits or signal lines SL. In some exemplary embodiments, the displayelement OLED may be an organic light-emitting diode. The display elementOLED may include a first electrode AE, a first organic layer HCL, anemission layer EML, a second organic layer ECL, and a second electrodeCE.

The first electrode AE may be disposed on the intermediate insulatinglayer VLD. The first electrode AE may be connected to the outputelectrode DE through a third contact hole CH3 penetrating theintermediate insulating layer VLD. The first electrode AE may be areflective electrode, without being limited thereto. For example, insome exemplary embodiments, the first electrode AE may be a transmissiveelectrode or a transflective electrode. When the first electrode AE is atransflective or reflective electrode, the first electrode AE mayinclude Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF/Ca,LiF/Al, Mo, Ti, or any compound or mixture thereof (e.g., a mixture ofAg and Mg). Alternatively, the first electrode AE may have amulti-layered structure including a reflective or transflective layerformed of the material mentioned above, and a transparent conductivelayer formed of indium tin oxide (ITO), indium zinc oxide (IZO), zincoxide (ZnO), indium tin zinc oxide (ITZO), or the like. For example, thefirst electrode AE may be a multi-layered metal layer having a stackedstructure of ITO/Ag/ITO.

In particular, when the first electrode AE is formed as a reflectiveelectrode, the first electrode AE may prevent external light frompassing through the emission area EA, and thus, suppress imagedistortion caused by the external light.

The pixel define layer PDL may include an organic material. The pixeldefine layer PDL is provided with a first opening OP1 definedcorresponding to the emission area EA. The first opening OP1 of thepixel define layer PDL exposes at least a portion of the first electrodeAE. The pixel define layer PDL is provided with a second opening OP2defined corresponding to the transmission area TA. The second openingOP2 of the pixel define layer PDL partially exposes a top surface of thecircuit element layer CL.

The transparent display panel DP may be provided with the emission areaEA and the non-emission area NEA adjacent to the emission area EA. Thenon-emission area NEA may surround the emission area EA. In someexemplary embodiments, the emission area EA may correspond to a portionof the first electrode AE exposed by the first opening OP1.

The first organic layer ECL may be an electron control layer. The firstorganic layer ECL may be disposed in common on the emission area EA andthe non-emission area NEA. In some exemplary embodiments, a commonlayer, such as the first organic layer ECL, may be formed in common on aplurality of display elements OLED. In some exemplary embodiments, thefirst organic layer ECL may include one or more of an electron injectionlayer and an electron transport layer.

The emission layer EML is disposed on the first organic layer ECL. Theemission layer EML may be disposed on a region corresponding to thefirst opening OP1. For example, the emission layer EML may be separatelyformed on each of the plurality of display elements OLED. The emissionlayer EML may include an organic material well known in the art. Forexample, the emission layer EML may be formed of one or more of amaterial emitting a red color, a material emitting a green color, and amaterial emitting a blue color, and may include a fluorescent orphosphorescent material.

FIG. 4 exemplarily shows a patterned emission layer EML, but theemission layer EML may be disposed in common on a plurality of displayelements OLED. When the emission layer EML is disposed in common on aplurality of display elements OLED, the emission layer EML may producewhite light. The emission layer EML may have a single-layered structuremade of a single material, a single-layered structure including aplurality of different materials, or a multiple-layered structureincluding a plurality of layers made of different materials.

The second organic layer HCL may be disposed on the emission layer EML.In some exemplary embodiments, the second organic layer HCL may beformed in common on a plurality of display elements OLED. The secondorganic layer HCL may be a hole control layer. The second organic layerHCL may include one or more of a hole injection layer and a holetransport layer.

The second electrode CE is disposed on the second organic layer HCL. Thesecond electrode CE is placed in common on a plurality of displayelements OLED. The second electrode CE may be formed of Ag, Mg, Al, Pt,Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or the like, but may be preferablyformed of Mg or an alloy thereof. The second electrode CE may have athickness of about 35 Å to about 80 Å.

Each of the first and second organic layers ECL and HCL has an openstructure corresponding to the transmission area TA. In addition, thesecond electrode CE may have the shape of an open structurecorresponding to the transmission area TA. For example, the first andsecond organic layers ECL and HCL may be removed from locationscorresponding to the transmission area TA, and the second electrode CEmay be removed from a location corresponding to the transmission areaTA. In this manner, on the transmission area TA, the top surface of thecircuit element layer CL may not be covered with but exposed by thefirst and second organic layers ECL and HCL and the second electrode CE.

The encapsulation layer TFE encapsulates the display element layer DPL.The encapsulation layer TFE is disposed on the second electrode CE. Theencapsulation layer TFE is placed in common on a plurality of displayelements OLED. In some exemplary embodiments, the encapsulation layerTFE directly covers the second electrode CE. In other exemplaryembodiments, a capping layer covering the second electrode CE may bedisposed between the encapsulation layer TFE and the second electrodeCE. In this case, the encapsulation layer TFE may directly cover thecapping layer. The encapsulation layer TFE may directly cover the topsurface of the circuit element layer CL exposed in the transmission areaTA.

The encapsulation layer TFE includes at least one inorganic layer(hereinafter, referred to as an encapsulation inorganic layer). Theencapsulation layer TFE may further include at least one organic layer(hereinafter, referred to as an encapsulation organic layer). Theencapsulation inorganic layer protects the display element layer DPLagainst moisture/oxygen, and the encapsulation organic layer protectsthe display element layer DPL against impurities, such as dustparticles. The encapsulation inorganic layer may include a siliconnitride layer, a silicon oxynitride layer, a silicon oxide layer, atitanium oxide layer, an aluminum oxide layer, or the like. Theencapsulation organic layer may include an acryl-based inorganic layer,without being limited thereto.

As illustrated in FIGS. 4 and 5, the non-emission area NEA is definedbetween the emission area EA and the transmission area TA, and the pixeldefine layer PDL is positioned on the non-emission area NEA. The pixeldefine layer PDL may include a first sidewall SW1 defining the emissionarea EA and a second sidewall SW2 defining the transmission area TA. Forexample, the first sidewall SW1 is disposed adjacent to the emissionarea EA, and the second sidewall SW2 is disposed adjacent to thetransmission area TA. Each of the first and second sidewalls SW1 and SW2has an inclined structure. For example, the first sidewall SW1 has aninclined structure sloped at a first angle θ1, and the second sidewallSW2 has an inclined structure sloped at a second angle θ2. The first andsecond angles θ1 and θ2 have different magnitudes from each other. Insome exemplary embodiments, the first angle θ1 may have a magnitudegreater than 0° and equal to or less than about 30°, and the secondangle θ2 may have a magnitude greater than about 30° and less than about90°.

Among a plurality of layers forming the display elements OLED, each ofthe first electrode AE and the emission layer EML may be separatelyprovided on a corresponding emission area EA. However, each of the firstorganic layer ECL, the second organic layer HCL, and the secondelectrode CE may be disposed in common on the emission area EA and thenon-emission area NEA. In some exemplary embodiments, each of the firstorganic layer ECL, the second organic layer HCL, and the secondelectrode CE may be formed in common on a plurality of emission areasEA, for example, on the first, second, and third emission areas (seeEA1, EA2, and EA3 of FIG. 3). Hereinafter, the layers ECL, HCL, and CEcommonly formed on a plurality of emission areas EA may collectively bereferred to as a common layer.

The first electrode AE and the emission layer EML may be disposed tooverlap the first sidewall SW1, and the common layer ECL, HCL, and CEmay be disposed to overlap the first and second sidewalls SW1 and SW2.Since the first sidewall SW1 is sloped at the first angle θ1 and thesecond sidewall SW2 is sloped at the second angle θ2 greater than thefirst angle θ1, a thickness of a portion of the common layer ECL, HCL,and CE overlapping the first sidewall SW1 may be different from athickness of a portion of the common layer ECL, HCL, and CE overlappingthe second sidewall SW2. For example, the thickness of the portion ofthe common layer ECL, HCL, and CE overlapping the second sidewall SW2may be less than the thickness of the portion of the common layer ECL,HCL, and CE overlapping the first sidewall SW1.

In some exemplary embodiments, the common layer ECL, HCL, and CE may notoverlap the transmission area TA. For example, the common layer ECL,HCL, and CE may be formed to have an open structure on the transmissionarea TA. In particular, since the second electrode CE of the commonlayer ECL, HCL, and CE has a low transmittance, removing the commonlayer ECL, HCL, and CE from the transmission area TA may increase atransmittance of the transparent display panel DP.

FIG. 6 is a cross-sectional view of a transparent display panelaccording to an exemplary embodiment. FIG. 7 is an enlarged view ofsection III of FIG. 6. The transparent display panel shown in FIGS. 6and 7 are substantially the same as that shown in FIGS. 4 and 5, andthus, repeated descriptions of the substantially the same elements willbe omitted to avoid redundancy.

Referring to FIGS. 6 and 7, a transparent display panel DP2 according anexemplary embodiment may have the display element layer DPL furtherprovided with a third electrode TE on the second electrode CE. The thirdelectrode TE may include a material having a transmittance of about 50%or higher. The third electrode TE may include a transparent conductiveoxide, a graphene, a nano-fiber, or the like. For example, the thirdelectrode TE may include one or more of ITO, IZO, ZnO, and In₂O₃.

The third electrode TE is electrically connected to the second electrodeCE. The third electrode TE may be a compensation electrode forcompensating a voltage drop (e.g., IR drop) caused by a reduction inthickness and area of the second electrode CE. In some exemplaryembodiments, the third electrode TE may have a thickness of about 50 Åto about 500 Å.

When the third electrode TE is includes a material, such as transparentconductive oxide having high transmittance, the third electrode TE maybe disposed to extend toward the transmission area TA. For example, thethird electrode TE may be formed in common on the emission area EA, thenon-emission area NEA, and the transmission area TA. As such, an area ofthe third electrode TE may be increased to improve a compensation effectfor the voltage drop. In addition, since the third electrode TE has ahigh transmittance, even when the third electrode TE is formed to extendtoward the transmission area TA, transmittance of the transparentdisplay panel DP2 may not be reduced.

As shown in FIGS. 6 and 7, the common layer ECL, HCL, and CE and thethird electrode TE may be disposed to overlap the first and secondsidewalls SW1 and SW2. Since the first sidewall SW1 is sloped at thefirst angle θ1 and the second sidewall SW2 is sloped at the second angleθ2 greater than the first angle θ1, a thickness of the common layer ECL,HCL, and CE overlapping the second sidewall SW2 may be less than athickness of the common layer ECL, HCL, and CE overlapping the firstsidewall SW1. Likewise, a thickness of the third electrode TEoverlapping the second sidewall SW2 may be less than a thickness of thethird electrode TE overlapping the first sidewall SW1.

In addition, the common layer ECL, HCL, and CE does not overlap thetransmission area TA. For example, the common layer ECL, HCL, and CE mayhave an open structure on the transmission area TA.

When the second sidewall SW2 has a steep angle or the third electrode TEhas a small thickness, the third electrode TE may be removed at aboundary between the transmission area TA and the non-emission area NEA.When the third electrode TE is formed of a material having a poor stepcoverage, the third electrode TE may be cut at the boundary between thetransmission area TA and the non-emission area NEA.

FIG. 8 is a plan view of a circuit configuration of each pixel of atransparent display panel according to an exemplary embodiment.

Referring to FIG. 8, each of the pixels PX1 and PX2 includes first,second, and third sub-pixels SPX1, SPX2, and SPX3. Each of the first,second, and third sub-pixels SPX1, SPX2, and SPX3 may include asub-pixel circuit SPC and a display element OLED. The display elementOLED may be an organic light-emitting diode, and may define emissionareas EA1, EA2, and EA3 on the sub-pixels SPX1, SPX2, and SPX3,respectively. The sub-pixel circuit SPC may be disposed to overlap acorresponding one of the emission areas EA1, EA2, and EA3. The sub-pixelcircuit SPC may overlap the non-emission area NEA. However, thesub-pixel circuit SPC does not overlap the transmission area TA.

In some exemplary embodiments, the sub-pixel circuit SPC may include twotransistors TR1 and TR2 and one capacitor Cst. However, the inventiveconcepts are not limited to a particular structure of the sub-pixelcircuit SPC, and in some exemplary embodiments, the numbers oftransistors and capacitors provided on the sub-pixel circuit SPC may bevariously changed.

The signal lines SL may be electrically connected to the sub-pixelcircuit SPC of each of the sub-pixels SPX1, SPX2, and SPX3. In someexemplary embodiments, the signal lines SL may include gate lines GL1,GL2, and GL3, data lines DL1, DL2, and DL3, and power voltage lines PL.Various signal lines other than the signal lines described above may beprovided based on the configuration of the sub-pixel circuit SPC.

As the sub-pixel circuits SPC of the first, second, and third sub-pixelsSPX1, SPX2, and SPX3 have the same circuit configuration, the sub-pixelcircuit SPC will be described with reference to the one included in thefirst sub-pixel SPX1 of the first pixel PX1.

The sub-pixel circuit SPC of the first sub-pixel SPX1 includes a firstthin film transistor TR1 connected to a first gate line GL1 and a firstdata line DL1, a second thin film transistor TR2 connected to the firstthin film transistor TR1 and the power voltage line PL, and a capacitorCst connected to the first thin film transistor TR1 and the second thinfilm transistor TR2. The first thin film transistor TR1 functions as aswitching transistor, and the second thin film transistor TR2 functionsas a drive transistor. The second thin film transistor TR2 iselectrically connected to the first electrode AE discussed above. InFIG. 8, the first thin film transistor TR1 and the second thin filmtransistor TR2 are illustrated as P-types, but the inventive conceptsare not limited thereto. For example, one of more of the first andsecond thin film transistors TR1 and TR2 may be formed as N-types.Furthermore, the numbers of thin film transistors and capacitors in thesub-pixel circuit SPC are not particularly limited, and in someexemplary embodiment, the sub-pixel circuit SPC may include two or morethin film transistors and one or more capacitors.

As shown in FIG. 8, the first gate line GL1 connected to the firstsub-pixel SPX1 extends in the first direction DR1 and is disposed tooverlap the non-emission area NEA. However, the present inventiveconcepts are not limited thereto, and in some exemplary embodiments, aportion of the first gate line GL1 may overlap the emission area EA.However, the first gate line GL1 may not overlap the transmission areaTA.

A second gate line GL2 connected to the second sub-pixel SPX2 extends inthe first direction DR1 and is disposed adjacent to the first gate lineGL1. The second gate line GL2 may be disposed in the non-emission areaNEA. The second gate line GL2 does not overlap the transmission area TA.For example, the second gate line GL2 may be disposed not to overlap thetransmission area TA, but rather bypass the transmission area TA. Insome exemplary embodiments, the second gate line GL2 may have a bentshape to bypass the transmission area TA. In other exemplaryembodiments, the second gate line GL2 may not be bent but issubstantially parallel to the first gate line GL1, as shown in FIG. 8.In this case, the transparent display panel DP may further include abridge line BL for electrical connection between the second gate lineGL2 and the second sub-pixel SPX2. The bridge line BL may not overlapthe transmission area TA, but overlap the non-emission area NEA and theemission area EA.

A third gate line GL3 connected to the third sub-pixel SPX3 may extendin the first direction DR1 and be disposed spaced apart in the seconddirection DR2 from the first and second gate lines GL1 and GL2 acrossthe transmission area TA. The third gate line GL3 overlaps thenon-emission area NEA, but not the transmission area TA.

The first data line DL1 may be connected in common to the first to thirdsub-pixels SPX1 to SPX3 of the first pixel PX1, and a second data lineDL2 may be connected in common to the first to third sub-pixels SPX1 toSPX3 of the second pixel PX2. The first and second data lines DL1 andDL2 overlap the non-emission area NEA, but not the transmission area TA.The power voltage line PL also overlaps the non-emission area NEA, butnot the transmission area TA. As discussed above, since the signal linesGL1 to GL3, DL1, DL2, and PL are disposed neither to penetrate nor tooverlap the transmission area TA, external light introduced into thetransmission area TA is not reflected by the signal lines GL1 to GL3,DL1, DL2, and PL, thereof the transmittance of the transparent displaypanel DP may not be reduced. Accordingly, a user may clearly recognizean object or image behind the transparent display panel DP.

FIGS. 9A to 9G are cross-sectional views showing a method ofmanufacturing a transparent display device according to an exemplaryembodiment. FIGS. 10A to 10C are enlarged cross-sectional views ofsection IV of FIGS. 9D to 9F, respectively.

Referring to FIG. 9A, a circuit element layer CL is formed on a topsurface of a base substrate BS. The circuit element layer CL may includea sub-pixel circuit provided on each sub-pixel and a plurality of signallines SL connected to the sub-pixel circuit. A third contact hole CH3may be formed in the circuit element layer CL, exposing an outputelectrode DE of a transistor TR.

FIG. 9A exemplarily shows a structure in which the circuit element layerCL is formed on each of an emission area EA, a non-emission area NEA,and a transmission area TA (see FIG. 9E), but the inventive concepts arenot limited thereto. For example, in some exemplary embodiments, atleast some layers included in the circuit element layer CL may beremoved from the transmission area TA.

Referring to FIG. 9B, on the circuit element layer CL, a first electrodeAE is formed corresponding to the emission area EA. The first electrodeAE may be in contact with the output electrode DE of the transistor TRthrough the third contact hole CH3. The first electrode AE may includeat least one of a transparent conductive material formed of ITO, IZO,ZnO, In₂O₃, etc., and a reflective electrode material formed of Ag, Mg,Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, etc. The first electrode AE maypartially overlap the non-emission area NEA.

Referring to FIG. 9C, a pixel define layer PDL is formed on the circuitelement layer CL and defines the emission area EA and the transmissionarea TA. The pixel define layer PDL may include a first opening OP1corresponding to the emission area EA and a second opening OP2corresponding to the transmission area TA. The first opening OP1 exposesat least a portion of the first electrode AE. A region where the firstelectrode AE is exposed may be defined as the emission area EA. Thesecond opening OP2 partially exposes a top surface of the circuitelement layer CL. When the circuit element layer CL is completelyremoved from the transmission area TA, a layer beneath the circuitelement layer CL may be exposed, or when a portion of the circuitelement layer CL is removed, a layer beneath the removed portion of thecircuit element layer CL may be exposed.

Referring to FIGS. 9D and 10A, a preliminary organic layer P_OL isformed, which may include an emission layer EML that corresponds to theemission area EA and disposed on the first electrode AE. The preliminaryorganic layer P_OL further includes a first preliminary organic layerP_ECL and a second preliminary organic layer P_HCL. The emission layerEML overlaps the emission area EA and the first electrode AE, while thefirst and second preliminary organic layers P_ECL and P_HCL overlap theemission area EA, the non-emission area NEA, and the transmission areaTA. The first and second preliminary organic layers P_ECL and P_HCL mayfurther overlap an emission area of a neighboring sub-pixel.

An electrode layer P_CE is formed on the preliminary organic layer P_OL.The electrode layer P_CE is formed to cover a top surface of the secondpreliminary organic layer P_HCL. The electrode layer P_CE may include ametallic material, such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li,or Ca. In some exemplary embodiments, the electrode layer P_CE may beformed of Mg or an alloy thereof. For example, the electrode layer P_CEmay have a thickness of about 35 Å to about 80 Å.

Referring to FIGS. 9E and 10B, the base substrate BS is disposed withthermal energy at a backside thereof. The process for supplying thethermal energy may be performed using a laser-induced thermal imageprocess, a flash mask transfer lithography process, an induction heatingprocess, or the like.

As shown in FIG. 9E, when a laser-induced thermal image process isperformed after a laser apparatus LD is disposed below the backside ofthe base substrate BS, the laser apparatus LD may provide thepreliminary organic layer P_OL with high-temperature light of about 300°C. to about 350° C., while moving in a first direction DR1. Thehigh-temperature light may be supplied in a scanning irradiation mode,in which light is irradiated every several microseconds (μs) from thelaser apparatus LD that is on the move.

On the emission area EA and the non-emission area NEA, the preliminaryorganic layer P_OL does not receive the high-temperature light from thelaser apparatus LD because the high-temperature light is reflected bythe signal lines SL, elements of the sub-pixel circuit (e.g., thetransistor TR), or the first electrode AE. However, because thetransmission area TA is not provided with a layer capable of reflectingthe high-temperature light, the preliminary organic layer P_OL mayreceive the high-temperature light without being reflected. Thehigh-temperature light supplied in the scanning irradiation modetemporarily heats up the preliminary organic layer P_OL positioned inthe transmission area TA.

The preliminary organic layer P_OL includes an organic material, whichhas a melting point lower than that of an inorganic material. As such,the organic material is likely to be heated up by the high-temperaturelight that is momentarily supplied, but other layers made of aninorganic material may not be heated up due to their high meltingpoints. A heated-up portion of the preliminary organic layer P_OL may belifted up from the top surface of the circuit element layer CL. As such,an air gap AG may be formed between the top surface of the circuitelement layer CL and the heated-up preliminary organic layer P_OL. Inthis manner, the heated-up portion of the preliminary organic layer P_OLby the thermal energy process may be easily separated from the circuitelement layer CL.

In other exemplary embodiments, an organic material layer of the circuitelement layer CL beneath the preliminary organic layer P_OL may beremoved from the transmission area TA. For example, an intermediateinsulating layer VLD may be opened at a portion corresponding to thetransmission area TA. The process in which the intermediate insulatinglayer VLD is opened at a portion corresponding to the transmission areaTA may be performed simultaneously with the formation of the thirdcontact hole CH3 discussed above.

In yet other exemplary embodiments, when the intermediate insulatinglayer VLD is remained on the transmission area TA, the intermediateinsulating layer VLD may be formed of an organic material having meltingpoint is higher than that of the preliminary organic layer P_OL.

Referring to FIGS. 9F and 10C, a transfer substrate TS may be placed onthe electrode layer P_CE. The transfer substrate TS may be a substrateon which an adhesive layer AL is formed in an area that corresponds tothe transmission area TA. When the adhesive layer AL is disposed tocorrespond to the transmission area TA, the heated-up portion of thepreliminary organic layer P_OL disposed on the transmission area TA maybe attached to a top surface of the adhesive layer AL, and then beseparated from the top surface of the circuit element layer CL as thetransfer substrate TS ascends. In this manner, the heated-up portion ofthe preliminary organic layer P_OL may be transferred onto the transfersubstrate TS.

Hence, as shown in FIG. 9G, a display element layer DPL may be formed onthe emission area EA and the non-emission area NEA, and be removed fromthe transmission area TA. Accordingly, the display element layer DPL maybe provided with a transmission part that exposes the top surface of thecircuit element layer CL on the transmission area TA.

Referring back to FIGS. 6 and 7, a third electrode TE may further beformed on the second electrode CE. The third electrode TE may include amaterial having a transmittance of 50% or higher. The third electrode TEmay include a transparent conductive oxide, a graphene, a nano-fiber, orthe like. For example, the third electrode TE may include one or more ofITO, IZO, ZnO, and In₂O₃.

The third electrode TE is electrically connected to the second electrodeCE. The third electrode TE may be a compensation electrode forcompensating a voltage drop (e.g., IR drop) caused by a reduction inthickness and area of the second electrode CE. In some exemplaryembodiments, the third electrode TE may have a thickness of about 50 Åto about 500 Å.

When the third electrode TE is made of a material, such as transparentconductive oxide having high transmittance, the third electrode TE maybe disposed to extend toward the transmission area TA. For example, thethird electrode TE may be formed in common on the emission area EA, thenon-emission area NEA, and the transmission area TA.

FIGS. 11A to 11C illustrate cross-sectional views showing a method offorming a pixel define layer of FIG. 9C.

Referring to FIG. 11A, the preliminary pixel define layer P_PDL isformed on the circuit element layer CL on which the first electrode AEis formed. The preliminary pixel define layer P_PDL may include apolymer resin. For example, the preliminary pixel define layer P_PDL mayinclude a polyacrylate-based resin or a polyimide-based resin. Thepreliminary pixel define layer P_PDL may further include an inorganicmaterial in addition to the polymer resin.

Referring to FIG. 11B, a photomask MS may be disposed on the preliminarypixel define layer P_PDL. The photomask MS may include alight-transmitting part FTA, a light-blocking part FBA, and a slit partHTA.

The light-transmitting part FTA is positioned to correspond to theemission area EA (see FIG. 4) and the transmission area TA (see FIG. 4),and allows provided light to pass therethrough in an exposure processusing the photomask MS. As such, an exposure process may expose aportion of the preliminary pixel define layer P_PDL, portion of whichcorresponds to the light-transmitting part FTA. As described above, whenthe preliminary pixel define layer P_PDL is directly exposed to anexposure process, the preliminary pixel define layer P_PDL may include aphotosensitive material.

The light-blocking part FBA is positioned to correspond to thenon-emission area (see NFA of FIG. 4), and shields light provided duringan exposure process. As such, the exposure process may not expose aportion of the preliminary pixel define layer P_PDL, portion of whichcorresponds to the light-blocking part FBA.

The slit part HTA is provided between the light-blocking part FBA andthe light-transmitting part FTA. The slit part HTA is a region includinga slit pattern, which causes light provided during an exposure processto have a lower transmittance than light passing through thelight-transmitting part FTA. As such, an exposure process may partiallyexpose a portion of the preliminary pixel define layer P_PDL, portion ofwhich corresponds to the slit part HTA.

Then, when exposure and development processes remove the exposed portionof the preliminary pixel define layer P_PDL, the pixel define layer PDLis formed as shown in FIG. 11C. The partial exposure through the slitpart HTA causes the pixel define layer PDL to have a first sidewall SW1having a gentle inclination angle. For example, the first sidewall SW1may have an inclined structure sloped at a first angle θ1 greater than0° and equal to or less than about 30°. The pixel define layer PDL mayhave a second sidewall SW2, which has an inclination angle greater thanthat of the first sidewall SW1, at a portion directly corresponding tothe light-transmitting part FTA and the light-shielding part FBA exceptfor the slit part HTA. In some exemplary embodiments, the secondsidewall SW2 may have an inclined structure sloped at a second angle θ2greater than about 30° and less than about 90°.

According to exemplary embodiments, a common layer may be removed from alocation corresponding to a transmission area, thereby increasing thetransmittance in the transmission area of the transparent displaydevice.

In addition, an inclination angle of a sidewall of a pixel define layermay be adjusted to simplify a process that removes the common layer fromthe location corresponding to the transmission area.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concepts are notlimited to such embodiments, but rather to the broader scope of theappended claims and various obvious modifications and equivalentarrangements as would be apparent to a person of ordinary skill in theart.

What is claimed is:
 1. A transparent display device comprising a basesubstrate and a plurality of pixels disposed on the base substrate, eachpixel having an emission area and a transmission area transparent toexternal light, each of the pixels comprising: a circuit element layerdisposed on the base substrate; a first electrode disposed on thecircuit element layer and corresponding to the emission area; a pixeldefine layer disposed on the circuit element layer, the pixel definelayer including a first sidewall defining the emission area and a secondsidewall defining the transmission area; an emission layer disposed onthe first electrode and corresponding to the emission area; and a secondelectrode disposed on the emission layer and including an opening thatcorresponds to the transmission area, wherein the first sidewall isinclined at a first angle, and wherein the second sidewall is inclinedat a second angle greater than the first angle.
 2. The transparentdisplay device of claim 1, wherein: the first angle of the firstsidewall is greater than 0° and equal to or less than about 30°; and thesecond angle of the second sidewall is greater than about 30° and lessthan about 90°.
 3. The transparent display device of claim 1, whereinthe second electrode has a thickness of about 35 Å to about 80 Å.
 4. Thetransparent display device of claim 1, further comprising: a firstorganic layer disposed between the first electrode and the emissionlayer, corresponding to the emission area, and having an opening in thetransmission area; and a second organic layer disposed between theemission layer and the second electrode, corresponding to the emissionarea, and having an opening in the transmission area.
 5. The transparentdisplay device of claim 1, further comprising a third electrode disposedon the second electrode and corresponding to the emission area.
 6. Thetransparent display device of claim 5, wherein the third electrodeincludes a material having a transmittance of at least 50%, and isdisposed to extend toward the transmission area.
 7. The transparentdisplay device of claim 6, wherein the third electrode has a thicknessof about 50 Å to about 500 Å.
 8. The transparent display device of claim1, wherein: each of the pixels has a plurality of sub-pixels; and theemission area includes a plurality of emission areas that respectivelycorrespond to the plurality of sub-pixels.
 9. The transparent displaydevice of claim 8, wherein the circuit element layer includes: asub-pixel circuit disposed on the plurality of emission areas; and aplurality of signal lines connected to the sub-pixel circuit.
 10. Thetransparent display device of claim 9, wherein the plurality of signallines do not overlap the transmission area.